ZERO PROCESS EFFLUENT DISCHARGE ATTAINED AT ST-LAURENT-PAPERBOARD-INC, MATANE, QUEBEC

From September 1994 to October 1995, St-Laurent Paperboard Inc., a cor rugated medium mill, situated at Matane, QC, has successfully undertak en and attained zero process effluent discharge. The process effluent flow was steadily decreased from 6000 m(3)/d to zero in October 1995. After optimization, the efficiency of the paper machine and the qualit y of the finished product were unchanged. The success of this project, linked to the proper design and installation of the equipment as well as our wet-end chemistry, is described. At zero discharge, the proces s water total dissolved solids reached equilibrium at about 12 000 mg/ L, while the conductivity stabilized at around 6000 mu S/cm. The non-c ontaminated effluent has the following characteristics: Total suspende d solids : 0.08 kg/t Biological oxygen demand : 0.03 kg/t Non-contamin ated effluent flow: 1.5 m(3)/t